Analysis of Sedimentation and Settling Process of Dense Alumina Slurries by Hydrostatic Pressure Measurement

A new evaluation technique has been developed for the characterization of slurry compressibility by hydrostatic pressure measurement. Slurry was poured into a test tube, and the change in hydrostatic pressure at the bottom was measured during the gravitational sedimentation. In order to investigate the effect of flocculation degree on the sedimentation behavior, pH values were changed using hydrochloric acid. It was found that the hydrostatic pressure of strongly flocculated slurry decreased faster than that of well-dispersed slurry. It was also shown that the hydrostatic pressure of weakly flocculated slurry decreased like well-dispersed slurry at initial stage of sedimentation, however it decreased rapidly after a certain time. This result suggests that the flocculation proceeded during the sedimentation for the weakly flocculated slurry. The results obtained from the hydrostatic pressure measurement were found to agree well with DLVO theory.